The recent increase in the world biofuels demand, along with the need to reduce costs while improving the environmental sustainability of the biodiesel production, have led to the search for catalysts that should be economically viable, efficient, and environmentally friendly. This paper reviews recent research and development of organic and inorganic tin catalysts; focusing on kinetic properties and catalytic activity in two key reactions for biodiesel production: free fatty acids (FFA) esterification and triglycerides (TG) transesterification. First the basic knowledge of homogeneous tin catalysts in esterification reactions of different carboxylic acids is provided. Second, main advances obtained in the study of FFA esterification reactions catalyzed by tin chloride are covered. The effect of the principal parameters of reaction on the yield and rate of alkyl esters production is described. Kinetic measurements allowed the determination of the activation energy (46.79？kJ？mol？1) and a first-order dependence in relation to both FFA and tin chloride catalyst concentration. Aspects related to recycling of the tin chloride catalyst in phase homogeneous are discussed. Third the advances obtained in the development of homogeneous catalysts based on tin complexes in transesterification reactions are summarized. Finally, results obtained from the use of tin organometallics compounds in reactions of vegetable oils transesterification reactions are concisely presented. The optimization of processes catalytic homogeneous utilized in the transesterification reactions can contribute to the improvement of the technology biodiesel production. 1. Introduction The demand for renewable energy sources has made biofuels an attractive alternative that can reduce the consumption of the traditional fossil fuels [1]. Biofuels have a closed loop for the CO2, that is, the main greenhouse gas and besides that they can contribute to the reduction in the emissions of toxic gases such as SO2, SO3, and CO [2]. Among the biofuels currently explored, biodiesel deserves highlights because it can be used pure or in blends with the diesel fuel. Biodiesel is a renewable fuel, biodegradable, and less polluting than diesel, obtained from the triglycerides transesterification (Figure 1) or esterification of free fatty acids (FFA) with short chain alcohol (methyl or ethyl alcohol) (Figure 2) [3]. Figure 1: Transesterification reaction of triglycerides (TG) for biodiesel production. Figure 2: Esterification reaction of fatty acids for biodiesel production. Biodiesel has been considered as a
References
[1]
A. Demirbas, “Political, economic and environmental impacts of biofuels: a review,” Applied Energy, vol. 86, no. 1, pp. S108–S117, 2009.
[2]
A. A. Kiss, A. C. Dimian, and G. Rothenberg, “Biodiesel by catalytic reactive distillation powered by metal oxides,” Energy and Fuels, vol. 22, no. 1, pp. 598–604, 2008.
[3]
A. Demirbas, “Comparison of transesterification methods for production of biodiesel from vegetable oils and fats,” Energy Conversion and Management, vol. 49, no. 1, pp. 125–130, 2008.
[4]
Y. Maeda, L. T. Thanh, K. Imamura et al., “New technology for the production of biodiesel fuel,” Green Chemistry, vol. 13, no. 5, pp. 1124–1128, 2011.
[5]
M. J. Haas, “Improving the economics of biodiesel production through the use of low value lipids as feedstocks: vegetable oil soapstock,” Fuel Processing Technology, vol. 86, no. 10, pp. 1087–1096, 2005.
[6]
L. T. Thanh, K. Okitsu, Y. Sadanaga, N. Takenaka, Y. Maeda, and H. Bandow, “A two-step continuous ultrasound assisted production of biodiesel fuel from waste cooking oils: a practical and economical approach to produce high quality biodiesel fuel,” Bioresource Technology, vol. 101, no. 14, pp. 5394–5401, 2010.
[7]
C. S. Cho, D. T. Kim, H.-J. Choi, T.-J. Kim, and S. C. Shim, “Catalytic activity of tin(II) chloride in esterification of carboxylic acids with alcohols,” Bulletin of the Korean Chemical Society, vol. 23, no. 4, pp. 539–540, 2002.
[8]
A. L. Cardoso, S. C. G. Neves, and M. J. da Silva, “Kinetic study of alcoholysis of the fatty acids catalyzed by tin chloride(II): an alternative catalyst for biodiesel production,” Energy and Fuels, vol. 23, no. 3, pp. 1718–1722, 2009.
[9]
A. L. Cardoso, S. C. G. Neves, and M. J. da Silva, “Esterification of oleic acid for biodiesel production catalyzed by SnCl2: a kinetic investigation,” Energies, vol. 1, no. 2, pp. 79–92, 2008.
[10]
A. L. Cardoso, R. Natalino, and M. J. da Silva, “Bioenrgy II: tin catalysed esterification of free fatty acids,” International Journal of Chemical Reactor Engineering, vol. 8, no. 1, pp. 1–12, 2010.
[11]
F. R. Abreu, D. G. Lima, E. H. Hamú, C. Wolf, and P. A. Z. Suarez, “Utilization of metal complexes as catalysts in the transesterification of Brazilian vegetable oils with different alcohols,” Journal of Molecular Catalysis A, vol. 209, no. 1-2, pp. 29–33, 2004.
[12]
D. A. C. Ferreira, M. R. Meneghetti, S. M. P. Meneghetti, and C. R. Wolf, “Methanolysis of soybean oil in the presence of tin(IV) complexes,” Applied Catalysis A, vol. 317, no. 1, pp. 58–61, 2007.
[13]
D. R. de Mendon？a, J. P. V. da Silva, R. M. de Almeida, C. R. Wolf, M. R. Meneghetti, and S. M. P. Meneghetti, “Transesterification of soybean oil in the presence of diverse alcoholysis agents and Sn(IV) organometallic complexes as catalysts, employing two different types of reactors,” Applied Catalysis A, vol. 365, no. 1, pp. 105–109, 2009.
[14]
S. Einloft, T. O. Magalh？es, A. Donato, J. Dullius, and R. Ligabue, “Biodiesel from rice bran oil: transesterification by tin compounds,” Energy and Fuels, vol. 22, no. 1, pp. 671–674, 2008.
[15]
T. M. Serra, D. R. de Mendona, J. P. V. da Silva, M. R. Meneghetti, and S. M. P. Meneghetti, “Comparison of soybean oil and castor oil methanolysis in the presence of tin(IV) complexes,” Fuel, vol. 90, no. 6, pp. 2203–2206, 2011.
[16]
A. Corma and H. García, “Lewis acids: from conventional homogeneous to green homogeneous and heterogeneous catalysis,” Chemical Reviews, vol. 103, no. 11, pp. 4307–4365, 2003.
[17]
M. J. Haas, K. M. Scott, W. N. Marmer, and T. A. Foglia, “The general applicability of in situ transesterification for the production of fatty acid esters from a variety of feedstocks,” Journal of the American Oil Chemists' Society, vol. 84, no. 10, pp. 963–970, 2007.
[18]
M. J. da Silva, C. E. Gon？alves, and L. O. Laier, “Novel esterification of glycerol catalysed by tin chloride (II): a recyclable and less corrosive process for production of bio-additives,” Catalysis Letters, vol. 141, no. 8, pp. 1111–1117, 2011.
[19]
K. Narasimharao, A. Lee, and K. Wilson, “Catalysts in production of biodiesel: a review,” Journal of Biobased Materials and Bioenergy, vol. 1, no. 1, pp. 19–30, 2007.
[20]
A. L. Cardoso, R. Augusti, and M. J. da Silva, “Investigation on the esterification of fatty acids catalyzed by the H3PW12O40 heteropolyacid,” Journal of the American Oil Chemists' Society, vol. 85, no. 6, pp. 555–560, 2008.
[21]
M. J. Berrios, J. Siles, M. A. Martín, and A. Martín, “A kinetic study of the esterification of free fatty acids (FFA) in sunflower oil,” Fuel, vol. 86, no. 15, pp. 2383–2388, 2007.
[22]
J.-Y. Park, Z.-M. Wang, D.-K. Kim, and J.-S. Lee, “Effects of water on the esterification of free fatty acids by acid catalysts,” Renewable Energy, vol. 35, no. 3, pp. 614–618, 2010.
[23]
M. L. da Silva, A. P. Figueiredo, A. L. Cardoso, R. Natalino, and M. J. da Silva, “Effect of water on the ethanolysis of waste cooking soybean oil using a tin(II) chloride catalyst,” Journal of the American Oil Chemists' Society, vol. 88, no. 9, pp. 1431–1437, 2011.
[24]
A. Srivastava and R. Prasad, “Triglycerides-based diesel fuels,” Renewable & Sustainable Energy Reviews, vol. 4, no. 2, pp. 111–133, 2000.
[25]
B. Freedman, R. O. Butterfield, and E. H. Pryde, “Transesterification kinetics of soybean oil,” Journal of the American Oil Chemists' Society, vol. 63, no. 10, pp. 1375–1380, 1986.
[26]
M. Canakci and J. Van Gerpen, “Biodiesel production via acid catalysis,” Transactions of the American Society of Agricultural Engineers, vol. 42, no. 5, pp. 1203–1210, 1999.
[27]
F. R. Abreu, D. G. Lima, E. H. Hamú, S. Einloft, J. C. Rubim, and P. A. Z. Suarez, “New metal catalysts for soybean oil transesterification,” Journal of the American Oil Chemists' Society, vol. 80, no. 6, pp. 601–604, 2003.
[28]
A. B. de Oliveira, I. F. Jorge, P. A. Z. Suarez, N. R. de S. Basso, and S. Einloft, “Synthesis and characterization of new bivalent tin chelate of 3-hydroxy-2-methyl-4-pyrone and its use as catalyst for polyesterification,” Polymer Bulletin, vol. 45, no. 4-5, pp. 341–344, 2000.
[29]
A. Casas, M. J. Ramos, J. F. Rodríguez, and á. Pérez, “Tin compounds as Lewis acid catalysts for esterification and transesterification of acid vegetable oils,” Fuel Processing Technology. In press.
[30]
Technical information: bulletin 345 revision 3/91, bulletin 346 revision 7/92 and bulletin 362 revision 10/93, Elf Atochem North America, Inc.
H. Noureddini and D. Zhu, “Kinetics of transesterification of soybean oil,” Journal of the American Oil Chemists' Society, vol. 74, no. 11, pp. 1457–1463, 1997.
[33]
F. R. Abreu, D. G. Lima, E. H. Hamú, C. Wolf, and P. A. Z. Suarez, “Utilization of metal complexes as catalysts in the transesterification of Brazilian vegetable oils with different alcohols,” Journal of Molecular Catalysis A, vol. 209, no. 1-2, pp. 29–33, 2004.
[34]
Y. C. Brito, D. A. C. Ferreira, D. M. de A. Fragoso et al., “Simultaneous conversion of triacylglycerides and fatty acids into fatty acid methyl esters using organometallic tin(IV) compounds as catalysts,” Applied Catalysis A, vol. 443-444, pp. 202–206, 2012.
